Re: A problem about static object in DLL
??????(Nocky Tian) schrieb:
In my DLL library, I declared a class in which there is a static object
of the same type, just like this.
class Object
{
......
public:
static const Object null;
};
The declaration is placed in a .h header file while the definition of
the static data member Object::null is placed in a .cpp source file as
the follows
const Object Object::null;
However, when I use the static object in my application project, a link
error is raised:
Error 1 error LNK2001: unresolved external symbol "public: static
struct ncs::Timestamp const ncs::Timestamp::null"
(?null@Timestamp@ncs@@2U12@B)Test2.objTest2If I place the definition of
the static member in the header file, it will be ok. But when I include
the header file in another file, another error occurred , which means
that the symbol Object::null is redefined!
It is correct to put "null" into the .cpp source file. However, you need to
export the variable so the linker can see it. Try something like:
__declspec(dllexport) const Object Object::null;
but you could be getting more problems when adding methods to the class. It
could be required that you declare the whole class __declspec(dllexport) or
__declspec(dllimport), you should google for something line "exporting a class
from a dll".
Norbert
I am puzzled seriously. How can I solve the problem?
Thanks in advance!
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